50 EVENINGS AT THE MICROSCOPE. 



rapidly running round like an endless band in some piece 

 of machinery ; only that the tooth points, as they run 

 by, remind one rather of a watch-wheel. For an instant 

 this appears, then the lips close again, and presently re- 

 open, and the tongue again performs its rasping. It is 

 wonderful to see ; — perhaps not more wonderful than 

 any other of God's great works, never more great than 

 when minutely great; but the action and the instrument, 

 the perfect way in which it works, and the effectiveness 

 with which the vegetation is cleared away before it, all 

 strike the mind with more than usual force, as exhibitions 

 of the skill of the Creator. 



As the Periwinkle moves along, mowing his sea-grass 

 as he goes, he carries before him two soft and flexible 

 horns, marked with zebra-like bands of black and white, 

 which he constantly waves about. These are organs of 

 some sense, probably of touch, and are therefore called 

 tentacles (or tryers) ; but they bear on their outer sides, 

 near the base, a pair of other organs, which are more 

 closely analogous to what we ourselves possess. You see 

 on each tentacle a little wart, which, when you look at it 

 with a lens, you perceive to have a round black glossy 

 extremity. This is the eye. By careful dissection under 

 the microscope, Ave find it to contain a beautiful trans- 

 parent crystalline lens, with a thick and glutinous vitreous 

 humour adhering to it behind, bounded by a retina or 

 curtain to receive the optic image, and an optic nerve. 



But much more attractive you will find the eyes in 

 this little Scallop. It is a half -grown individual of what 

 is provincially known as the Squin (Pecten opercidaris), 

 much prized for its delicate flavour. Belonging to the 

 bivalve class of the Mollusca, the animal is inclosed 

 within two shallow shelly plates, concave internally and 

 convex externally, which are united by a hinge, just as the 

 works of a watch are protected by the case. When the 

 little creature is at its ease, as when the water is pure 



